1. Field of the Invention
The present invention relates to an image detecting device which is preferably used in a medical radiological diagnosis apparatus such as a dental X-ray panoramic tomography imaging apparatus, or an industrial nondestructive inspection apparatus, and also to a medical X-ray imaging apparatus using the image detecting device.
2. Description of the Related Art
In a dental X-ray panoramic tomography imaging apparatus, conventionally, an X-ray image which passes through a long and narrow slit and moves in a direction perpendicular to the longitudinal direction of the slit is taken while changing the light-receiving position in accordance with the movement of the image, as disclosed in, for example, Japanese Examined Patent Publication JP-B2 2-229329 (1990), and Japanese Unexamined Utility Model Publication JPU 4-80507 (1992). Japanese Unexamined Patent Publication JPA 3-259569 (1991) discloses a configuration in which a plurality of X-ray detecting elements are arranged in a staggered pattern and the arrangement pitch of light receiving elements is matched so as to receive X-ray fan beams. In the prior aft disclosed in JP-B2 2-29329, the imaging process is conducted by using a single X-ray image sensor. In the prior aft disclosed in JPU 4-80507, an X-ray image is formed on a scintillator using a fluorescent screen, and the image converted to visible light is guided by optical fiber bundles to a plurality of CCD image detecting elements, where the X-ray image is detected. The fluorescent face of the scintillator is partitioned into plural regions arranged in the longitudinal direction of the slit. An end face of each optical fiber bundle is joined to the regions and the CCD image detecting elements are disposed on the other end face of the optical fiber bundles, respectively.
FIG. 7 shows the configuration for detecting an X-ray image which is disclosed in JPU 4-80507. The fluorescent screen 1 constituting the scintillator converts incident X-rays into visible light. The slit for the X-ray panoramic tomography imaging has a long and narrow shape of, for example, 6 mm.times.150 mm, and practical CCD image detecting devices have a length of about 50 mm. Consequently, the surface of the fluorescent screen 1 is partitioned into three image regions 2, 3, and 4 which are arranged in the longitudinal direction of the slit. The CCD image detecting elements 8, 9, and 10 detect the image from the image regions 2, 3, and 4 through the optical fiber bundles 5, 6, and 7, respectively.
In the prior art disclosed in JPA 2-29329, since the single X-ray imaging element is used, it is difficult to take an image of a large slit, or the like. In the prior art disclosed in JPA 3-259,569, the plural X-ray imaging elements are arranged in a staggered pattern, and hence images detected by adjacent X-ray imaging elements are shifted in position and time from each other. Even when the images are subjected to an electrical signal processing, therefore, it is difficult to accurately reproduce the image.
In the prior art disclosed in JPU 4-80507, it is possible to take an image of the longitudinally elongating image region. However, since the boundaries of the image regions which are obtained by partitioning the fluorescent screen are formed in the image moving direction, images positioned in the boundaries cannot be sufficiently detected.
As shown in FIG. 8, each of the optical fiber bundles 5, 6, and 7 is formed by bundling a plurality of optical fibers 11. The end faces in the axial direction of each optical fiber 11 can be polished and aligned. When a side face of the optical fiber bundle 5, 6, or 7 is polished in a bundled state, however, some of the optical fibers 11 may be broken. Therefore, the optical fiber bundles 5, 6, and 7 cannot be subjected to a polishing process, and remain in a bundled state.
As a result, as shown in FIG. 9, each side face of the optical fiber bundle 5, 6, or 7 is not always in a perfectly aligned state, and inevitably has a somewhat rugged face. In the boundaries of the image regions 2, 3, and 4 where such optical fiber bundles 5, 6, and 7 are adjacent to each other, a gap 12 is often formed, so that the detection of an image 15 passing through the gap 12 is more difficult than that of images 13 and 14 passing through normal regions.
The diameter of each optical fiber 11 is smaller than the size of a light receiving element of the CCD image detecting elements 8, 9, and 10, so that plural optical fibers 11 correspond to one light receiving element. Therefore, the gap 12 is not formed when all the optical fibers 11 are initially bundled so as to conform to the fluorescent screen 1 shown in FIG. 7, and then divided into the optical fiber bundles 5, 6, and 7 in accordance with the image regions 2, 3, and 4 so as to be respectively distributed to the CCD image detecting elements 8, 9, and 10. However, it is impossible to cleanly divide the optical fibers 11 without damaging the optical fibers because the optical fibers are very thin. When some of the optical fibers 11 are once damaged, images in the vicinity of the boundaries of the image regions 2, 3, and 4 cannot be detected.